Patent Document 1 discloses a technology for an active anti-vibration supporting device. According to the known technology described in Patent Document 1, computed is a target lift amount of a movable member of an actuator of an active control mount, based on outputs from an engine rotation speed sensor, a load sensor, and an acceleration sensor in one vibration cycle of an engine.
Then, based on the computed target lift amount, determined is the duty ratio of a duty group that controls a drive current to be output to the actuator in the next vibration cycle. Simultaneously, also determined is a phase delay, which is the timing of the start of the duty group.
Then, in further subsequent vibration cycles, based on the first, the second, the third, . . . duty groups computed correspondingly to the lengths T1, T2, T3, . . . of vibration cycles of the engine vibration, the actuator of the active anti-vibration supporting device is driven. As the lengths T1, T2, T3, . . . , of the vibration cycles of the engine gradually become shorter with increase in the rotation speed of the engine, a current supplied to the actuator does not become zero at the respective ends of the first, second, third, . . . duty groups. Consequently, the peak value of the current gradually increases, which not only disables an effective anti-vibration function of the active anti-vibration supporting device, but also causes a possibility that the actuator generates heat.
In this situation, according to the known technology described in Patent Document 1, in a case, for example, that that the overlapping amount between the first and second duty groups exceeds a threshold value, the duty ratio of the second duty group is set to zero so that supply of current to the actuator is stopped.